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Abstract
Trials of ground-based, multi-channel microwave radiometers were conducted in Hong Kong for several months in 2004 and 2006. Following these trials, a permanent unit has been installed in Hong Kong since February 2008. The present paper discusses the performance and nowcasting applications of this instrument during the past year. A number of temperature and humidity retrieval methods have been tried out in the study period and the seasonal retrieval method based on linear regression of historical data is found to have the best performance in comparison with co-located radiosonde data. The integrated water vapour and liquid water path measurements from the radiometer are found to have generally good correlation with radiosonde and weather radar data respectively. For nowcasting applications, K-index is calculated from the temperature and humidity profiles from the radiometer. It turns out to have good correlation with the integrated water vapour, which could only be studied using the continuously thermodynamic profiles available from the radiometer. Moreover, the average K-index in rain episodes is found to have reasonable correlation with the total number of lightning flashes within about 20 km from the radiometer, a proxy of the instability of the atmosphere, similar to the study results of Chan and Tam (2005).